As the UK wakes up to the longest day of the year today, campaigners are calling for more sunshine in our lives – by urging the government to keep British Summer Time (BST) all year round.

Maintaining daylight saving time would save energy and 450,000 tonnes of carbon a year, according to new research, and reduce road accidents, saving the NHS £200m annually.

The Lighter Later initiative, which is being coordinated by the 10:10 climate change campaign, would see a permanent shift to daylight saving time. Under the proposals, the clocks would not revert to Greenwich Mean Time (GMT) this autumn, but from next year, the clocks would continue in the same pattern of "spring forward, fall back", shifting an hour of daylight from the morning to the evening through the year.

Dr Elizabeth Garnsey, from the University of Cambridge, will present her study from the peer-reviewed journal, Energy Policy, at a parliamentary launch today.

Garnsey found that winter demand peaked at sunset and then around 5.30pm, when people were returning from work. The increased energy demand is met by reserve energy generation, such as oil, which is expensive and polluting.

Daily demand in the UK would be reduced by at least 0.3% if daylight saving time were continued after October, her study found.

This would amount to 450,000 tonnes of carbon saved annually, or the equivalent of taking 200,000 cars off the road.

"We need better alignment with the way people spend their time," Dr Garnsey said. "At 4.30am on 21 June most people will still be asleep – that's an average of three hours' wasted daylight."

Garnsey said that, compared with other measures to reduce greenhouse gas emissions through energy efficiency and renewable technology, changing the clocks would be extremely cheap.

She said: "Advancing the clocks would be a one-off administrative change and would save energy in all succeeding years. Many ways of reducing carbon emissions inevitably need investment in new infrastructure, none of which are required to advance the clocks."

Garnsey and Lighter Later, which is also supported by the Royal Society for the Prevention of Accidents (RoSPA) and the Tourism Alliance, say that the change would lower fuel bills, increase tourism and reduce crime and obesity – and save lives as evening visibility improves during rush hour. In a related report, Garnsey includes estimates that up to 450 serious injuries and 104 deaths annually could be prevented by abolishing GMT, potentially saving the NHS £200m a year.

"Traffic is heavier for longer in the early evening than in the morning. Consequently an hour of light at evening rush hour reduces risk for more drivers and pedestrians than an hour of light during the shorter morning rush hour, when there are fewer road users than at the end of the working day."

She also addressed concerns over an increased risk to children on the way to school in Scotland. The concerns were raised during a previous trial when the country stuck to GMT+1 all year round.

"In the trial period between 1968 and 1971, it was reported in Hansard that there was a net reduction of deaths on the roads of 3% in England and 8.6% in Scotland. But folk memory has become shaped by tragic accidents that happened in the morning. The media didn't report the reduction in the afternoon and never corrected it."

She added that no one had made the case for keeping GMT as it was. "GMT was not set to save electricity or prevent accidents. It's sundial technology and policy inertia is the only thing preventing this change."

Eugenie Harvey, director of 10:10 UK, said: "In the UK we love our long summer days. Lighter evenings make us happier, healthier and safer. After today the nights will start drawing in again."

Benefits:

• Conservative estimate of 450,000 tonnes of C02 saved annually

• In Britain 450 serious injuries and 104 deaths annually could be prevented on the roads, saving the NHS £200m a year in treatment costs

• Decrease in crime and greater safety for the elderly

• Average of 55 minutes increase in extra daylight for outdoor activities